In a UMTS (Universal Mobile Telecommunications System) network, a GGSN (Gateway General Packet Radio Service Support Node) typically has an inactivity timer for each established PDP (Packet Data Protocol) context. A mobile device can communicate with the UMTS network over an active PDP context. However, if the inactivity timer expires, the GGSN initiates PDP context deactivation to release the PDP context. The mobile device can re-establish the PDP context; however, excessively re-establishing the PDP context places a burden on the UMTS network.
Existing approaches involve the mobile device periodically transmitting packets over the PDP context so as to maintain the PDP context. However, in certain circumstances, the transmitting is too frequent and results in unnecessary activity. This can cause an overload situation for the network or cause radio resource shortages if many of such mobile devices are concentrated in a small area such as a cell or cell sector.
In order to provide “always-on” experience for end users, some UMTS networks have functionality to preserve the PDP context while releasing the associated radio resource when no data traffic is expected (see 3GPP TS25.060). Since radio resources are not tied to the PDP context when no traffic is expected, a network operator may configure the inactivity timer in the GGSN to have a large value, or may remove the inactivity timer altogether. In such cases, it could be wasteful in terms of UMTS network resources for mobile devices to periodically transmit data at an interval which is much shorter than the inactivity timer.
Regardless of the length of data transmitted by the mobile device, the mobile device and the network exchange many signalling or control messages to establish and release an RRC (Radio Resource Control) connection, a signalling connection, a PDP context and a radio bearer. Moreover, the radio resources (e.g. downlink scrambling code) will remain allocated for a while after the data transmission is completed, e.g. 15 seconds. When a large number of mobile devices are concentrated in single cell, the periodic transmission of short data could impact the radio network and radio resources.